Qualitative studies of vote buying find the practice to be common in many Latin American countries, but quantitative studies using surveys find little evidence of vote buying. Social desirability bias can account for this discrepancy. We employ a survey-based list experiment to minimize the problem. After the 2008 Nicaraguan municipal elections, we asked about vote-buying behavior by campaigns using a list experiment and the questions traditionally used by studies of vote buying on a nationally representative survey. Our list experiment estimated that 24% of registered voters in Nicaragua were offered a gift or service in exchange for votes, whereas only 2% reported the behavior when asked directly. This detected social desirability bias is nonrandom and analysis based on traditional obtrusive measures of vote buying is unreliable. We also provide systematic evidence that shows the importance of monitoring strategies by parties in determining who is targeted for vote buying.